Reactor for carrying out a reaction between two fluid starting materials over a catalyst bed with premixing of the fluid starting materials in a mixing-in device

ABSTRACT

A reactor ( 1 ) for carrying out a reaction between two fluid starting materials ( 2, 3 ) over a catalyst bed ( 4 ) with premixing of the fluid starting materials ( 2, 3 ) before introduction into the catalyst bed within a delay time of less than 150 ms in a mixing-in device ( 5 ), wherein the mixing-in device ( 5 ) is made up of the following elements which are arranged essentially transverse to the inflow direction of the first fluid starting material stream ( 2 ):
         two or three rows arranged behind one another of tubes ( 6 ) which have turbulence generators on the outside and constrict the flow cross section for the first fluid starting material stream ( 2 ) to from ½ to 1/10, with the second fluid starting material stream ( 3 ) being passed through the interiors of the tubes ( 6 ) and injected via openings ( 7 ) in the tubes ( 6 ) into the first fluid starting material stream ( 2 ), and   a perforated plate ( 10 ) upstream of the tubes ( 6 ) and   a perforated plate ( 11 ) downstream of the tubes ( 6 ),
 
is proposed.

The invention relates to a reactor for carrying out a reaction betweentwo fluid starting materials over a catalyst bed with premixing of thefluid starting materials in a mixing-in device, a mixing-in device forthe reactor and also a use.

In chemical engineering, there are a number of processes in which twofluid starting materials are premixed and subsequently reacted over acatalyst bed. For the reaction to proceed uniformly here, it isnecessary to have very homogeneous premixing at frequently very shortpermissible residence times, often below 150 ms or below 50 ms, beforethe reaction mixture is contacted with the catalyst and the latter takesover control of the course of the reaction.

To achieve this demanding object, mixing-in devices which achieve a veryhigh mixing quality in a very short time, i.e. mixing-in devices havinga very low construction height L/D, where L is the length of themixing-in device in the flow direction of the main fluid and D is theinflow area of the catalyst bed perpendicular to the flow direction ofthe main fluid, are required.

Known mixing-in devices for reactors through which flow is axial, i.e.in the direction of their longitudinal axis, achieve at best aconstruction height L/D of four. Such a device is known, for example,from DE-A 10 2004 024 957, according to which a reaction gas is injectedaxially, i.e. in the longitudinal direction of the reactor, via a bundleof gas feed tubes which are fixed to the tube plates at both ends andare provided with inlet openings for oxygen which is introduced into theintermediate space around the gas feed tubes into an axial flow reactorin which a catalyst bed is located.

In comparison, it was an object of the invention to provide a reactorand a mixing-in device according to which virtually 100% mixing of twofluid starting materials is achieved in a premixing step before theseare fed to a catalyst bed, with a greatly reduced length of themixing-in device in the flow direction of the main fluid and thus withachievement of very short residence times.

The object is achieved by a reactor for carrying out a reaction betweentwo fluid starting materials over a catalyst bed with premixing of thefluid starting materials before introduction into the catalyst bedwithin a delay time of less than 150 ms in a mixing-in device, whereinthe mixing-in device is made up of the following elements which arearranged essentially transverse to the inflow direction of the firstfluid starting material stream:

-   -   two or three rows arranged behind one another of tubes which        have turbulence generators on the outside and constrict the flow        cross section for the first fluid starting material stream to        from ½ to 1/10, with the second fluid starting material stream        being passed through the interiors of the tubes and injected via        openings in the tubes into the first fluid starting material        stream, and    -   a perforated plate upstream of the tubes and    -   a perforated plate downstream of the tubes.

In a preferred embodiment, it has been found that the use of commercialfinned tubes known as heat exchangers which have been modified slightlyby providing openings in the channels between the fins make it possibleto utilize the intermediate spaces of the channels between the fins asvirtually ideal mixing chambers with high turbulence by injecting afirst fluid starting material stream essentially perpendicular to thefinned tubes and a second fluid starting material stream through theinteriors of the finned tubes by the openings in the channels into thefirst fluid starting material stream.

The term fluid refers, in a known manner, to all liquids, vapors andgases which obey the hydrodynamic laws of nonsolid continua. The fluidstarting materials in the present case are, in particular, gaseous orliquid starting materials, preferably gaseous starting materials. Thefluid starting materials can each comprise one or more substances.

The volume flows of the two fluid starting materials are frequently verydifferent, which makes the mixing task correspondingly difficult: themass flow of the second fluid starting material can, in particular, befrom 1 to 30% of the mass flow of the first fluid starting materialsteam, or from 5 to 20% of this.

The catalyst bed is made up of solid catalyst particles, i.e. thecatalyst is a catalyst which is heterogeneous in respect of the fluidstarting materials. The solid catalyst particles can preferably form afixed catalyst bed or, in a further preferred embodiment, a movingcatalyst bed.

The catalyst bed can in the case of upright cylindrical reactors beintroduced in a horizontal or vertical layer. There can also be aplurality of catalyst beds. The catalyst, generally in the form offree-flowing shaped bodies, can be introduced into holding devices, forexample catalyst baskets. The holding devices can more preferably beformed by support gratings, woven meshes, edge slit screens, etc.

The reaction gas mixture flows into the catalyst bed from the side of aninflow face of the bed and leaves the catalyst bed via an outflow face.

According to the invention, a mixing-in device for the fluid startingmaterials to be reacted, which comprises the following elements:

-   -   two or three rows arranged behind one another of tubes which        have turbulence generators on the outside and    -   a perforated plate upstream of the tubes and    -   a perforated plate downstream of the tubes,        is provided upstream of the inflow face of the catalyst bed.

The fluid starting materials are premixed in the mixing-in device.Premixing is understood in the present case to be a mixing prior toentrance into the catalyst bed.

The turbulence generators arranged on the outside of the tubes can bestructures of various geometries, but it is essential that they increasethe turbulence in the fluids flowing around the tubes. They arepreferably elements as are known for static mixers or as packingelements for distillation columns or, for example, crossed strips ofmetal sheet.

The tubes having turbulence generators on the outside are preferablyfinned tubes.

Finned tubes are known in chemical engineering and are used, inparticular, as heat exchanger tubes. Finned tubes and their productionare described, for example, in DE-A 1 950 246 or DE-A 2 131 085.

A finned tube is a tube, generally a metal tube, which have acylindrical exterior to which elongated strips, viz. the fins, areattached along a longitudinal edge, generally by welding. The fins arefrequently attached in a spiral or helical fashion to the exterior ofthe tube, but can also be attached in the longitudinal direction ofthis. They normally have a smooth continuous surface but can also beperforated. They can be continuous but can also, advantageously, be cutto a fin base to form segments. Cut fins are particularly suitable forincreasing the turbulence. The segments here can have variousgeometries, for example in the form of rectangles, trapezoids, etc. Thecuts between the segments can be configured with or without removal ofmaterial. The segments can particularly advantageously be rotated orslanted at an angle to the fin base in order to increase the turbulence,in particular in the regions between the fins, viz. the channels, bymeans of an angle of incidence and accordingly improve the mixingaction.

A dense arrangement of fins over the length of the tube is advantageous;in particular, from 100 to 300 turns of the fins can be provided permeter of tube length.

Tubes having an external diameter in the range from 25 to 150 mm, inparticular from 20 to 50 mm, are advantageously used.

The tin height based on the external diameter of the tubes isadvantageously in the range from 1/10 to ½.

The fin thickness can advantageously be from 0.3 to 1.5 mm.

In the case of cut fins, it is advantageous to form segments having awidth of from 3 to 12 mm, preferably from 4 to 8 mm.

The tubes can have any cross section, for example circular, oval orpolygonal, for example triangular.

The finned tubes are arranged parallel to one another in rows, with onerow of finned tubes being able to be located in a plane or arrangedalong a radius of a circle.

The arrangement of the finned tubes depends, in particular, on theintended flow in the reactor:

In the case of axial flow apparatuses in which the reaction mixture isconveyed in the direction of the longitudinal axis of the frequentlycylindrical reactor, the catalyst bed or the catalyst beds are arrangedhorizontally along a reactor cross section. Correspondingly, the rows offinned tubes which form part of the mixing-in device have to be arrangedessentially parallel to the catalyst beds, in a cross-sectional plane ofthe reactor.

In the case of radial flow reactors having a radial flow direction ofthe reaction gas mixture, one or more catalyst beds are arranged in theform of a hollow cylinder having a wall thickness appropriate to the bedthickness in suitable accommodation devices, for example baskets. On theinflow side of the catalyst bed, which can be on the inside or theoutside, the finned tubes are arranged along a circle concentric withthe catalyst bed.

It has been found that two or three rows of finned tubes are suitablefor the mixing task according to the invention.

In a preferred embodiment the composition of the second fluid startingmaterial stream can be different in the individual rows of finned tubes.Especially, it is possible to feed into the first row of finned tubes asecond fluid starting material stream with a defined composition andinto the second row of finned tubes a second fluid starting materialstream with a composition different therefrom.

Here, it is advantageous to arrange the second row of finned tubes nextto the gaps between the first and, in the case of three rows of finnedtubes, arrange the third row of finned tubes next to the gaps in thesecond row of finned tubes. A heat transfer medium can advantageouslyflow through the second row and, if appropriate, the third row of finnedtubes. It is also possible for the second and, if appropriate, thirdrows of finned tubes to be formed by solid material of any crosssection.

Finned tubes of the same geometry should be used within a row of finnedtubes, but the geometry can also vary within the rows of finned tubes.

The finned tubes have in each case at least two diametrically oppositeopenings per channel of fins on the exterior of the tubes forming themin the channels between the fins; these openings are located at thepositions which are closest to the respective adjacent finned tube inthe row of finned tubes. The second fluid starting material is injectedthrough these openings in the channels between the fins into the firstfluid starting material. In this way, a large number of small-scalemixing chambers having a high turbulence are thus made available in thechannels, in particular in the case of fins cut to form segments, withthis effect being able to be increased further by slanted setting of thefin segments. An excellent quality of mixing in the micro range isachieved in this way.

A concentric plug-in tube having outflow openings arranged atappropriate intervals on the exterior can in each case be advantageouslyprovided in the interior of the finned tubes in order to predistributethe second fluid starting material stream over the length of the tubeand thus also to ensure a largely equalized temperature of this.

The second fluid starting material stream is preferably introduceduniformly into the finned tubes via a ring line as a main distributorand particularly preferably via two ring lines at each end thereof.

The above ring lines can more preferably in turn be supplied via in eachcase a further additional ring line, preferably having a larger diameterand arranged outside the abovementioned ring lines.

The rows of finned tubes are preceded by a perforated plate which islikewise arranged perpendicular to the inflow direction of the firstfluid starting material stream and thus essentially parallel to theplane formed by the rows of finned tubes, in particular in the case ofthe axial flow reactor, or on a circle concentric with the rows offinned tubes, particularly in the case of the radial flow reactor.

The upstream perforated plate has openings whose total area based on thecross-sectional area of the inflow of the first fluid starting materialsteam is less than or equal to 0.5, in particular less than or equal to0.3.

The upstream perforated plate is advantageously located at a distancefrom the inflow face of the first row of finned tubes which correspondsto from seven to twenty times the diameter of the openings in theupstream perforated plate.

The diameter of the openings in the upstream perforated plate isadvantageously smaller than half of the clear spacing of the finsbetween two successive turns.

Particularly in the case of axial flow reactors, the upstream perforatedplate can be omitted if it is ensured that the gas stream is distributedlargely uniformly over the reactor cross section.

The mixing-in device has a second perforated plate which is locateddownstream in the outflow direction from the device and has openingswhose diameter is greater than or equal to the diameter of the upstreamperforated plate.

Perforated plates are predominantly flat components having openings ofany cross section.

The ratio of the thickness of the two perforated plates, viz. theupstream and downstream perforated plates, based on the diameter of theopenings in the perforated plates, is preferably in the range from 0.75to 2.0.

The downstream perforated plate is advantageously arranged at a distanceof from 0.75 to 2.0 times the diameter of the finned tubes of the lastrow of finned tubes from the outflow plane of the last row of finnedtubes.

The downstream perforated plate is advantageously located at a distancecorresponding to from 5 to 20 times the diameter of the openings in thedownstream perforated plate from the entry into the catalyst bed.

The material for the finned tubes and the perforated plates ispreferably stainless steel; materials which are resistant to oxidationand, if appropriate, carbonization at elevated temperature areparticularly preferred.

The mixing-in device is arranged essentially transverse to the flowdirection of the first fluid starting material stream. This means thatthe first fluid starting material stream is introduced in the directionof the normals to the main extension of the mixing-in device which canbe flat as in the case of axial flow reactors, or curved, as in the caseof radial flow reactors.

However, the term essentially transverse also encompasses deviationsfrom the normals of ±5° or ±10° or even ±30°.

The mixing-in device can at construction depths, i.e. a distance betweenthe upstream perforated plate and the downstream perforated plate, inthe range from 100 to 200 mm achieve excellent, virtually 100% mixingwith a pressure drop in the first fluid starting material stream,frequently the reaction gas, in the order of 20 mbar and a pressure dropin the second fluid starting material stream, frequently anoxygen-comprising stream which for safety reasons alone has to be underat least slightly superatmospheric pressure, in the range from about 50to 100 mbar.

An extremely large number of points of injection of the second fluidstarting material stream into the first fluid starting material streamin the order of 10 000 points of injection per m² is achieved.

The invention also provides a mixing-in device for a reactor of the typedescribed above, which comprises the above-described elements: two orthree rows of tubes provided which have turbulence generators, inparticular finned tubes, an upstream perforated plate and a downstreamperforated plate.

The above-described reactor and the mixing-in device are particularlysuitable for carrying out reactions of a first gaseous reaction mixturewith an oxygen-comprising gas stream, for example air, in particular forcarrying out oxydehydrogenations of hydrocarbons, for example propane orbutane, for the partial oxidation of natural gas by means of air, fordesulfurization, for catalytic cracking or generally for reactions knownas chemical conversion.

The invention also provides a static mixer for two or more fluids, whichis composed of the elements of the above described mixing-in device,which are arranged essentially transverse to the inflow direction of thefirst fluid starting material stream:

A reactor for carrying out a reaction between two fluid startingmaterials over a catalyst bed with premixing of the fluid startingmaterials before introduction into the catalyst bed within a delay timeof less than 150 ms in a mixing-in device, wherein the mixing-in deviceis made up of the following elements which are arranged essentiallytransverse to the inflow direction of the first fluid starting materialstream:

-   -   two or three rows arranged behind one another of tubes which        have turbulence generators on the outside and constrict the flow        cross section for the first fluid starting material stream to        from ½ to 1/10, with the second fluid starting material stream        being passed through the interiors of the tubes and injected via        openings in the tubes into the first fluid starting material        stream, and    -   a perforated plate upstream of the tubes and    -   a perforated plate downstream of the tubes.

The mixer is not limited to the type of the fluids to be mixed. Thefluids can be especially gases or liquids, preferably gases. The fluidsto be mixed can each comprise one or more substances. These need notreact chemical with each other.

The mixer can show all the embodiments which are described in theproceeding for the mixing-in-device.

The mixer is especially build-up in a modular type, i.e., the number oftubes in the two or three rows arranged behind one another can beextended according to requirements, practically without limits, so thatit is possible to make available inflow areas from a few squarecentimeters to arbitrary dimensions, for example of several 100 m².

The static mixer is cost and energy advantageous, producible fromelements commercially available. It shows a small height for a highlyhomogenous mixing (mixing quality >99.9%), with ultra short mixing time,<50 ms, for two or more fluids.

The invention is described in more detail below with the aid of adrawing and an example.

In the Drawing:

FIG. 1A shows a segment of a section through a radial flow reactoraccording to the invention having a flow direction of the first fluidstarting material stream from the inside outward,

FIG. 1B shows a view analogous to FIG. 1A but with the flow direction ofthe first fluid starting material stream from the outside inward,

FIG. 2A shows a detail of a finned tube, with depiction of an individualfin and the procedures for producing it in FIG. 2B and a cross sectionthrough a finned tube in FIG. 2C,

FIG. 3 shows a perspective view of a finned tube,

FIG. 4A shows a longitudinal section through a preferred embodiment of afinned tube, with depiction of a cross section in FIG. 4B,

FIG. 5A shows a preferred embodiment of a radial flow reactor accordingto the invention, with flow from the inside outward and a depiction ofthe cross section in FIG. 5B,

FIG. 5C shows a further embodiment of a radial flow reactor according tothe invention with flow from the outside inward,

FIG. 6 shows a further preferred embodiment of a radial flow reactoraccording to the invention,

FIG. 7A shows a preferred embodiment of an axial flow reactor accordingto the invention, with depiction of a detail of the mixing-in device inFIG. 7B, and

FIG. 8 shows a longitudinal section through an experimental module fordetermining the quality of mixing.

In the figures, identical reference numerals denote identical orcorresponding features.

FIG. 1A shows a segment of a cross section through a first embodiment ofa radial flow reactor 1 according to the invention with introduction ofa first fluid stream 2 via the interior of the reactor and outflow ofthis at the outer wall of the reactor. The first fluid starting materialstream 2 impinges perpendicularly onto a mixing-in device 5 comprisingtwo rows of finned tubes 12 which are arranged so that the tubes arelocated next to the gaps in the other row and are preceded in the flowdirection by a first perforated plate 10 and are followed by a secondperforated plate 11. The two rows of finned tubes 12 and the upstreamperforated plate 10 and the downstream perforated plate 11 are eacharranged on concentric circles. The reaction mixture which has beenpremixed in the mixing-in device 5 subsequently flows through thecatalyst bed 4.

FIG. 1B shows a segment of the cross section through a further radialflow reactor according to the invention, but with the difference fromthat in FIG. 1A that the flow of the first fluid starting materialstream 2 is from the outside inward. Accordingly, the mixing-in device 5comprising two rows of finned tubes 12 and an upstream perforated plate10 and a downstream perforated plate 11 is, because it is upstream ofthe catalyst bed 4, arranged along circles having a greater radius thanthe catalyst bed 4.

FIGS. 2A to 2C show details of finned tubes 12 having openings 7 whichare arranged diametrically opposite to one another in the channels 8between the fins 9 of the finned tubes 12. Here, FIG. 2B shows a fin 9which is divided by cuts down to a rib base 14 into segments 13 and FIG.2C shows a cross section through a finned tube 12 with tube 6, channels8 and segments 13.

FIG. 3 shows a perspective view of a finned tube 12 with tube 6 andhelical fin 9 which is divided, with the exception of a continuous finbase 14, into segments 13.

FIG. 4A shows a longitudinal section through a finned tube 12 with tube6 and fins 9, with openings 7 in the channels 8 between the fins 9 ofthe finned tubes 12. In the interior of the tube, there is a concentriccentral plug-in tube 17 which has openings 18, which can be seen in thecross section in the plane B-B in FIG. 4B, and by means of which thesecond fluid starting material stream 3 is distributed in thelongitudinal direction of the finned tubes 12. In FIG. 4A, one end ofthe finned tube 12 is provided with a ring distributor 19 for the secondfluid starting material stream 3.

FIG. 5A shows a longitudinal section through a radial flow reactor withintroduction of the first fluid starting material stream 2 through thecentral interior space of the reactor and discharge at the outer wall ofthe reactor 1.

FIG. 5B clearly shows, in addition to the annular arrangement ofcatalyst bed 4 and mixing-in device 5 in the cross section, the centralcross section 20 through which the first fluid starting material stream2 flows.

The reactor depicted in longitudinal section in FIG. 5C is analogous tothe reactor of FIG. 5A, but with introduction of the first fluidstarting material stream 2 from the outside inward and correspondinglywith the mixing-in device 5 being arranged outside the catalyst bed 4.

FIG. 6 depicts a further preferred embodiment of a reactor 1 accordingto the invention with flow of the second fluid starting material stream3 from the outside inward and with displacement bodies 21 in the centralinterior space and at the reactor wall, which displacement bodies canpreferably be, as shown in the figure, parabolic.

FIG. 7A shows a longitudinal section through an axial flow reactorhaving catalyst beds 4 and mixing-in devices 5 arranged in planes, withdepiction of a longitudinal section in FIG. 7A and a detail of alongitudinal section in a plane perpendicular to the plane depicted inFIG. 7A in FIG. 7B. The detail in FIG. 7B shows two rows of finned tubes12 with openings 7 for exit of the second fluid starting material stream3 from the interior of the finned tubes 12, with additionalpredistribution of the further fluid starting material stream 3 viacentral plug-in tubes 17 having openings 18, and also an upstreamperforated plate 10 and a downstream perforated plate 11.

FIG. 8 shows a longitudinal section through an experimental module fordetermining the quality of mixing, which has two rows of finned tubes 6,with central plug-in tubes 17 having openings 18, upstream perforatedplate 10 and downstream perforated plate 11, and also having anexchangeable catalyst bed 4 and a measuring rod 22 for measuring theconcentration which can be pulled out.

EXAMPLE

The mixing quality of model gases, namely a first main gas streamconsisting of nitrogen and a second gas stream consisting of nitrogenand 10% by volume of carbon dioxide and having a 10-fold lower volumeflow compared to the main gas stream, was determined by means of theexperimental module shown in FIG. 8. The mixing-in device comprised tworows of finned tubes 12 which were arranged so that the tubes of one rowwere next to the gaps in the other row, with each row consisting ofthree tubes 6 having an external diameter of 31.7 mm and a helical fin 9which went around the tube 17 times and was cut into segments having awidth of 4 mm and a height of 6.4 mm. An upstream perforated plate 10having an opening ratio of 5% was arranged at a distance of 15 mm fromthe inflow plane of the first row of finned tubes 12 and a downstreamperforated plate having an opening ratio of likewise 5% was arranged ata distance of likewise 15 mm from the outflow plane of the second row offinned tubes.

The concentration of carbon dioxide in the stream of nitrogen wasdetermined by infrared absorption using a UNOR 6N instrument fromMaihak, Hamburg. To rule out calibration uncertainties, a 20 m longpiece of tubing was attached to the end of the measuring rod and gas forreference measurement was introduced into the instrument just before theend of the tubing. The reference measurement indicated precisely 1% byvolume of carbon dioxide.

To determine the quality of mixing produced by the mixing-in device ofthe invention comprising finned tubes, an upstream perforated plate anda downstream perforated plate, the measuring rod 22 was continuouslypushed through the apparatus and samples were taken at intervals of 2 mmand the carbon dioxide concentration of these was determined by infraredabsorption using the abovementioned instrument. Measured values rangingfrom 0.99% by volume of carbon dioxide and 1.01% by volume of carbondioxide, i.e. deviations of not more than ±1% from the value of thereference measurement, and thus excellent mixing over the entire crosssection of the apparatus were measured.

LIST OF REFERENCE NUMERALS

-   1 reactor-   2 first fluid starting material-   3 second fluid starting material-   4 catalyst bed-   5 mixing-in device-   6 tubes-   7 openings in the tubes 6-   8 channels-   9 fins-   10 upstream perforated plate-   11 downstream perforated plate-   12 finned tube-   13 segments-   14 fin base-   15 openings in 10-   16 openings in 11-   17 central plug-in tube-   18 openings in the central plug-in tube 17-   19 ring distributor-   20 cross section through which the first fluid starting material    stream flows-   21 displacement body-   22 measuring rod

1. A reactor (1) for carrying out a reaction between two fluid startingmaterials (2, 3) over a catalyst bed (4) with premixing of the fluidstarting materials (2, 3) before introduction into the catalyst bedwithin a delay time of less than 150 ms in a mixing-in device (5),wherein the mixing-in device (5) is made up of the following elementswhich are arranged essentially transverse to the inflow direction of thefirst fluid starting material stream (2); two or three rows arrangedbehind one another of tubes (6) which have turbulence generators on theoutside and constrict the flow cross section for the first fluidstarting material stream (2) to from ½ to 1/10, with the second fluidstarting material stream (3) being passed through the interiors of thetubes (6) and injected via openings (7) in the tubes (6) into the firstfluid starting material stream (2), and a perforated plate (10) upstreamof the tubes (6) and a perforated plate (11) downstream of the tubes(6).
 2. The reactor (1) according to claim 1, wherein the tubes (6)which have turbulence generators on the outside are finned tubes (12),with the turbulence generators being configured as fins (9) and theopenings (7) opening into the tubes (6) in the channels (8) between thefins (9).
 3. The reactor (1) according to claim 1 or 2, wherein thefinned tubes (12) constrict the free flow cross section for the firstfluid starting material stream (2) to from ⅓ to ⅙ of its original size.4. The reactor (1) according to any of claims 1 to 3, wherein the finnedtubes (12) are formed by tubes (6) which have a cylindrical exterior andhave fins (9) which consist of elongated strips and are welded along alongitudinal edge of the strip in a spiral fashion onto the exterior ofthe tube and are cut with the exception of a fin base (14) to formsegments (13).
 5. The reactor (1) according to claim 4, wherein thesegments (13) are rotated at an angle to the fin base (14).
 6. Thereactor (1) according to any of claims 1 to 5, wherein the finned tubes(12) have from 100 to 300 turns of the fins (9) per meter length of thetube (6).
 7. The reactor (1) according to any of claims 1 to 6, whereinthe tubes (12) have an external diameter in the range from 25 to 150 mm,preferably in the range from 20 to 50 mm.
 8. The reactor (1) accordingto any of claims 1 to 7, wherein the ratio of the height of the fins (9)to the external diameter of the tubes (12) is in the range from 1/10 to½.
 9. The reactor (1) according to any of claims 1 to 8, wherein thefins (9) have a thickness in the range from 0.3 to 1.5 mm and thesegments (13) have a width in the range from 3 to 12 mm, preferably inthe range from 4 to 8 mm.
 10. The reactor (1) according to any of claims1 to 9, wherein the second row of finned tubes (6) is arranged so thatthe tubes of this row are located next to the gaps in the first row offinned tubes (6).
 11. The reactor (1) according to claim 10 which hasthree rows of finned tubes (6), with the third row of finned tubes (6)being arranged so that the tubes are located next to the gaps in thesecond row of finned tubes (6).
 12. The reactor (1) according to any ofclaims 1 to 11, wherein a heat transfer medium flows through the secondrow and, if appropriate, the third row of finned tubes (6) or the secondand, if appropriate, third rows are formed by solid material of anycross section.
 13. The reactor (1) according to any of claims 1 to 12which has in each case two openings (7) per channel (8) between the fins(9) of the finned tubes (6) in diametrically opposite positions on thechannels (8), with the minimum distance to the adjacent finned tube (6)in the row of finned tubes.
 14. The reactor (1) according to any ofclaims 1 to 13, wherein the upstream perforated plate (10) is arrangedat a distance corresponding to from 7 to 20 times the diameter of theopenings (15) in the upstream perforated plate (10) from the inflowplane of the first row of finned tubes (6) for the first fluid startingmaterial (2).
 15. The reactor (1) according to any of claims 1 to 14,wherein the diameter of the openings (15) in the upstream perforatedplate (10) is smaller than half of the clear spacing of the fins betweentwo successive turns.
 16. The reactor (1) according to any of claims 1to 15, wherein the opening ratio in the upstream perforated plate (10)defined as the sum of the free areas of the openings (15) in theperforated plate based on the total cross-sectional area perpendicularto the inflow direction of the first fluid starting material stream (2)into the mixing-in device (5) is ≦0.5, preferably ≦0.3.
 17. The reactor(1) according to any of claims 1 to 16, wherein the ratio of thethickness of the perforated plate to the diameter of the openings (15,16) in the perforated plate (10, 11) is in the range from 0.75 to 2.0.18. The reactor (1) according to any of claims 1 to 17, wherein thedownstream perforated plate (11) is located at a distance of from 0.5 to2 times the diameter of the finned tubes (6) of the last row of finnedtubes (6) from the outflow plane of the finned tubes (6).
 19. Thereactor (1) according to any of claims 1 to 18, wherein the diameter ofthe openings (16) in the downstream perforated plate (11) is greaterthan or equal to the diameter of the openings (15) in the upstreamperforated plate (10).
 20. The reactor (1) according to any of claims 1to 19, wherein the distance from the downstream perforated plate (11) tothe entry of the reaction mixture into the catalyst bed (4) correspondsto from 5 to 20 times the diameter of the openings (16) in thedownstream perforated plate (11).
 21. The reactor (1) according to anyof claims 1 to 20, wherein materials which are resistant to oxidationand, if appropriate, carbonization at elevated temperature are used asmaterial for the tubes (6) and the perforated plates (10, 11).
 22. Amixing-in device (5) for a reactor (1) according to any of claims 1 to21.
 23. A process for carrying out chemical reactions between two fluidstarting materials (2, 3) over a catalyst bed (4) in a reactor (1)according to any of claims 1 to 21, wherein the first fluid startingmaterial stream (2) is a reaction gas mixture and the second fluidstarting material stream (3) is an oxygen-comprising gas stream, inparticular for carrying out oxydehydrogenations.
 24. Static mixer fortwo or more fluids, characterized in, that it is composed of theelements of the mixing-in device (5) according to claim 22, which arearranged essentially transverse to the inflow direction of the firstfluid starting material stream (2): two or three rows arranged behindone another of tubes (6) which have turbulence generators on the outsideand constrict the flow cross section for the first fluid startingmaterial stream (2) to from ½ to 1/10, with the second fluid startingmaterial stream (3) being passed through the interiors of the tubes (6)and injected via openings (7) in the tubes (6) into the first fluidstarting material stream (2), and a perforated plate (10) upstream ofthe tubes (6) and a perforated plate (11) downstream of the tubes (6).